This invention relates to methods of processing of dried samples for subsequent analysis. Blood samples stored as dried blood spots have emerged as a useful sampling and storage vehicle for clinical and pharmaceutical analysis in a wide range of applications. For example, the Newborn Screening Ontario facility at the Children's Hospital of Eastern Ontario evaluates dried blood spot samples from approximately 140,000 babies each year for 28 inherited diseases. In each screening test, a dried blood spot sample is collected and then mailed to facility for analysis by tandem mass spectrometry (MS/MS). Unfortunately, this technique is slowed by an extensive sample preparation regimen (including excision/punching, extraction, evaporation, resolubilization, and derivatization), and in addition, high-throughput screening typically requires robotic sample handling.
The success of dried blood spot sampling and MS/MS for newborn screening has led to a surge in popularity for similar techniques for a wide spectrum of applications in clinical labs and the pharmaceutical industry. Dried blood spot sampling methods allow for the collection of small amounts of sample and are convenient for long-term storage and cataloguing. MS/MS methods allow for the unambiguous identification and quantification of many different analytes in a single shot.
Unfortunately, the throughput and turn-around-time associated with this technique are problematic as a result of time-consuming sample preparation. In particular, the off-line sample preparation of blood spots on filter paper necessitates the labor intensive and time consuming steps of extraction via centrifugation, in which the analyte is obtained in a supernatant. Furthermore, the maintenance of instruments (sample preparation robots and mass spectrometers) and plumbing (capillary tubes and associated connections) requires many hours of laboratory-time, which reduces the throughput of such analyses. In addition, the costs are magnified by the scale of operation (for example, nearly 150,000 samples are processed a year in Ontario alone).